The Aircraft Endurance Challenge

[gridghost]

@Van Disaster @Gman_builder After installing SVE (clouds), Scatterer and KER, i seem to get more resonable length, still too long though. (added some beautyshots  )

 

[Van Disaster]

Almost home. So "excited" I took it supersonic to try and get it done

[Van Disaster]

And down, flight of the Icarus is finally over.

Spoiler

13 Kerbin days, 1 hour, 28 mins, 124,467km over ground, that's 33 ( sidereal ) circumnavigations. I am guessing from how fuel consumption was progressing that it'd probably have managed 200k km - I dumped most of the remaining fuel before landing & I'd burnt a fair bit doing a supersonic lap.

@gridghostIf that issue isn't in the bug tracker already & it's still like that in stock, I'd really recommend raising it with Squad just in case it's related to the orbit changes.

 

Edited July 9, 2016 by Van Disaster

[Gman_builder]

@Van DisasterWow thats impresssive!

7 hours ago, gridghost said:

@Van Disaster @Gman_builder After installing SVE (clouds), Scatterer and KER, i seem to get more resonable length, still too long though. (added some beautyshots  )

 

Thats also a different plane though so.

19 hours ago, Baybrawler said:

Are we allowed to use drop tanks? Also, is timewarp allowed to make the flight faster?

 

Thank you,

Baybrawler

Drop tanks are allowed but i advise against time warp. Bad things can come from time warp.

[gridghost]

@Van Disaster Ya, i'll do that. And Day-um... But naming the flight after one that ended in disaster seems out of place  This one ended in triumph.

@Gman_builder Ya, and the other one did 1300 m/s and 9.1 kkm. This one did 1200 m/s and 6.7 kkm. The first one should have had a shorter distance @1300 m/s and -3 minutes.

Fact of the matter is that the length of a circumnavigation (or any flight really) seems to be tied to CPU/GPU power (at least in the 64bit windows-build of v1.1.3). When using mods doing calculations in the background and added visuals, i got 2.4 kkm less in a plane that should've travelled a longer distance. I chose to use SVE, KER and scatterer because i saw both you and Van Disaster using it or similar mods.

But as you stated before, it's probably still more accurate to calculate the distance from flight-time and average speed.

And BTW, what do you think of the Big Bird as a plane? It's more or less a heavy fighter w/o any weapons (and getting 24.7 kkm from a fighter must be some kind of record, don't you think  )

Edited July 9, 2016 by gridghost

[Van Disaster]

If distance calc issues like that are showing up it's most definitely a bug somewhere and it *definitely* shouldn't be FPS related - physics calcs are meant to happen at fixed intervals ( every 20ms ) whereas the visual stuff gets updated when it can be.

I named it with a gentle sort of irony

[gridghost]

13 minutes ago, Van Disaster said:

If distance calc issues like that are showing up it's most definitely a bug somewhere and it *definitely* shouldn't be FPS related - physics calcs are meant to happen at fixed intervals ( every 20ms ) whereas the visual stuff gets updated when it can be.

I named it with a gentle sort of irony

Not FPS-related, but GPU related as the GPU, if loaded, uses more CPU-cycles to handle throughput. More so if it is an integrated GPU. And loading the CPU seems to be what KSP needs to not give way crazy numbers. It's still not correct tho. Even when playing around with the Physics-time-delta thingie...

I thought about locking the FPS, because of earlier forays into moddable games, where the physics-calculations were framebased, way back in the day

[Gman_builder]

41 minutes ago, gridghost said:

Not FPS-related, but GPU related as the GPU, if loaded, uses more CPU-cycles to handle throughput. More so if it is an integrated GPU. And loading the CPU seems to be what KSP needs to not give way crazy numbers. It's still not correct tho. Even when playing around with the Physics-time-delta thingie...

I thought about locking the FPS, because of earlier forays into moddable games, where the physics-calculations were framebased, way back in the day

Maybe changing the Physics Delta-Time Per second or whatever it called in the main menu settings will affect the distance. I don't really know what that setting does but it sounds fancy and seems to sound like it has something to do with time time and distance per second.

[Cunjo Carl]

5 hours ago, Gman_builder said:

Maybe changing the Physics Delta-Time Per second or whatever it called in the main menu settings will affect the distance. I don't really know what that setting does but it sounds fancy and seems to sound like it has something to do with time time and distance per second.

  That slider shouldn't affect distance much. It just affects at what point KSP will start lagging your game to fit in the additional physics calculations for bigger ships. If you push the value too high you can get phys-warp-like floppyness at 1x speed with the trade-off of tasty lag reduction! It's handy for enhancing some glitches too, but shouldn't do much to stable planes.

  Speaking of stable planes, I've grown accustomed to the gentle drone of mine running in the background over the last few days. I'm positively buzzing with excitement, but even with time warp it could still be a while before I have the final results.

   I've been writing some simple KOS scripts for autopiloting, altitude maintenance, avoiding mountains, and tweaking throttle for fuel savings. KOS's built in autopilot is impressively strong and versatile! If anyone has requests and it's within my skill level, I'd be happy to drum something up. It'll be a fun diversion while waiting for this thing to run out of fuel.

   Also, I'm happy your 1.1.3 is quite stable, but mine has been crashing constantly! I have 20 crash logs from the last week and a half alone. It's kindof a truism with PC games that mileage may vary when it comes to stability, and this patch has been a particularly rough one for my computer. Still, I've been saving often so not too much time gets lost.... except when it does  .

[Gman_builder]

3 hours ago, Cunjo Carl said:

  That slider shouldn't affect distance much. It just affects at what point KSP will start lagging your game to fit in the additional physics calculations for bigger ships. If you push the value too high you can get phys-warp-like floppyness at 1x speed with the trade-off of tasty lag reduction! It's handy for enhancing some glitches too, but shouldn't do much to stable planes.

  Speaking of stable planes, I've grown accustomed to the gentle drone of mine running in the background over the last few days. I'm positively buzzing with excitement, but even with time warp it could still be a while before I have the final results.

   I've been writing some simple KOS scripts for autopiloting, altitude maintenance, avoiding mountains, and tweaking throttle for fuel savings. KOS's built in autopilot is impressively strong and versatile! If anyone has requests and it's within my skill level, I'd be happy to drum something up. It'll be a fun diversion while waiting for this thing to run out of fuel.

   Also, I'm happy your 1.1.3 is quite stable, but mine has been crashing constantly! I have 20 crash logs from the last week and a half alone. It's kindof a truism with PC games that mileage may vary when it comes to stability, and this patch has been a particularly rough one for my computer. Still, I've been saving often so not too much time gets lost.... except when it does  .

The stability of your game also reflects the stability of your system. If your rig is custom built or there is a lot of bottlenecking between components it could lead to a unstable system and game. My Dell XPS 13 Notebook laptop has a better CPU and more RAM than my old custom built desktop but it is much more unstable from the factory. I get monthly bluescreens and random glitches and bugs for seemingly no reason. On the other hand my desktop has a Asus GTX 960 OC 4GB Turbo GPU, 4gb RAM, a Intel Quad Q2800 clocking at 2.33 ghz. Where my laptop i5 clocks at 3.7 ghz. So the desktop is a lot slower but I have never had a single game crash in this build of KSP. I don't really know why my desktop system is more stable than my factory laptop but it just is and that is what matters lol.

[zolotiyeruki]

@Van Disaster - how did  you get up to near-mach-1 speeds? I'm building a (hopefully more efficient) craft of similar mass, but I can't get above about mach 0.45.

For anyone who understand the Aero GUI better than I, I'm confused by the last line there--L-I-D.  That stands for "lift-induced drag", right?  Why does that number seem to increase with altitude, even with a relatively constant airspeed?

[Cunjo Carl]

2 hours ago, zolotiyeruki said:

@Van Disaster - how did  you get up to near-mach-1 speeds? I'm building a (hopefully more efficient) craft of similar mass, but I can't get above about mach 0.45.

For anyone who understand the Aero GUI better than I, I'm confused by the last line there--L-I-D.  That stands for "lift-induced drag", right?  Why does that number seem to increase with altitude, even with a relatively constant airspeed?

I'm just going to toss out a guess here, but hopefully @Van Disaster can correct me if I'm wrong. If you keep the same airspeed but go to a higher altitude, you'll need to assume a higher AoA (angle of attack) to maintain enough lift to keep a level flight. As you increase your AoA beyond 4.5 degrees, your lift induced drag will increase relative to your lift. So it's not the higher altitude per-say, but the greater AoA that causes the most difference.

Though this makes good hypothetical sense to me, I haven't actually tested out your plane, and I don't have a quantitative knowledge of how AeroGUI handles the calculation of L-I-D. Still, hopefully it's nice food for thought?

Totally unnecessary for having fun with designing, but for a mathematical description of LID, we can crack into the KSP physics files...

Spoiler

I say 'crack into', but really they made it in plain text, which is like the nicest thing ever. Thanks Squad! You can find the physics file in the main KSP folder, and it's very instructive to poke around. How drag and lift are influenced by angle of attack is determined by a pair of arrays labled 'lift' and 'drag' under the 'lifting surfaces' section. These unlabelled numbers can be converted into plots using some fancy (but easy) math, and I've provided those values and plots here. These plots show L/D which is closely related to your changes in LID. You'll also notice that I plot 'useful lift', which takes into account that not all of your lift is in the useful up direction... some of it winds up pointing backwards like drag .

KSP's numbers.

Getting useful values.

Pretty plots!

If you'd like more information, I'd be happy to help.

 

Edit: Slightly lower AoAs are better, more in the 2-3ish degrees ballpark should be optimal. I took into account the reduction of lift due to the tilted direction of AoA, but not the increase in drag. I'll be posting new plots when I have a chance to photo them tomorrow.

Edited July 11, 2016 by Cunjo Carl
Forgot a math.

[Gman_builder]

1 hour ago, zolotiyeruki said:

@Van Disaster - how did  you get up to near-mach-1 speeds? I'm building a (hopefully more efficient) craft of similar mass, but I can't get above about mach 0.45.

For anyone who understand the Aero GUI better than I, I'm confused by the last line there--L-I-D.  That stands for "lift-induced drag", right?  Why does that number seem to increase with altitude, even with a relatively constant airspeed?

@Cunjo Carlis absolutely right. Why can't you get a plane above Mach 0.45? You can get to Mach 0.9 on a single Juno if you do it right!

[Cunjo Carl]

3 minutes ago, Gman_builder said:

@Cunjo Carlis absolutely right. Why can't you get a plane above Mach 0.45? You can get to Mach 0.9 on a single Juno if you do it right!

@zolotiyeruki Along those lines, If you'd like you can post a few pictures of your craft and we can help debug. Struggling through designing difficulties is part of the joy of KSP, but it's also an experience easy to overdo, huh! The most common issues for me have been: Occluded air-intake/engine, going too high, having superfluous things hanging off, and going too high. I listed going too high twice because it's super easy to do with the Juno. Trust me, I've been there with the "why doesn't my Juno go faster" struggles!

Juno spaceplanes - The Spacecraft Exchange

[Van Disaster]

Pics are the thing yep. Keep your AoA down, that is quite an efficiency killer.  I had a couple of degrees of incidence on my main wings ( enough that the thing took off & landed flat, like a B52 ). You can see my AoA in most of the pics, it's on the PA panel as well as FAR. Anything over 1.8 ( aside from when the thing was fully loaded ) and I'd be dropping a little altitude to bring it down again. I flew on the drag number on the FAR panel - that directly translates to fuel use.

Keeping critical mach up as high as possible was fairly important too, because the faster you go the lower the AoA at the same altititude. Given I was intending travelling a bit over critical mach, the lowish wave drag helped a lot. I'm pretty sure that turbofan confuses FAR's wave drag calcs a bit.

I got the thing up to M1.25 in the end, was hoping to get over the transonic drag hump completely but it didn't quite manage it. I spent a fair bit of time bringing wave drag down as low as I could get it with that brick of an engine too.

Edited July 11, 2016 by Van Disaster

[zolotiyeruki]

Yeah, I usually put a 5 degree AoA on my lifting surfaces and use Pilot Assistant to maintain level flight, so the fuselage is at 0 pitch and the wings are at 5 degrees.  Is there a way to get exact (or at least repeatable) <5 degree rotations on parts in the SPH?  I've revised my design a bit by eliminating a bunch of fuel, and so it now flies faster (Mach 0.75 or so), but still at the bottom of the hump.  As I type, it's KER is showing just shy of 3 days' worth of fuel (and climbing, as the craft climbs and the thrust drops).

[Van Disaster]

There's a mod called Part Angle Display which I'm not sure works with 1.1.3 ( as I didn't try it ). I just turned off angle snap & let it rotate a couple of lumps, nothing special. 5 degrees might be a bit much ( for FAR, at least. Stock, probably not ).

One other thing, watch your trim like a hawk. Pitch controls should be there to change pitch, not hold it.

Edited July 11, 2016 by Van Disaster

[zolotiyeruki]

3 hours ago, Van Disaster said:

There's a mod called Part Angle Display which I'm not sure works with 1.1.3 ( as I didn't try it ). I just turned off angle snap & let it rotate a couple of lumps, nothing special. 5 degrees might be a bit much ( for FAR, at least. Stock, probably not ).

One other thing, watch your trim like a hawk. Pitch controls should be there to change pitch, not hold it.

Yeah, the pitch trim is something I learned a while back--shifting around fuel can result in surprisingly large efficiency gains.

I wonder how the efficiency of your craft would be affected if flown in stock aero.  I haven't used FAR at all, so all my aero optimizations are based on the quirks of the stock model.  Does FAR let you decrease drag by clipping parts, like you did with the tanks on top of your fuselage?

Edited July 11, 2016 by zolotiyeruki

[Gman_builder]

8 hours ago, zolotiyeruki said:

Yeah, I usually put a 5 degree AoA on my lifting surfaces and use Pilot Assistant to maintain level flight, so the fuselage is at 0 pitch and the wings are at 5 degrees.  Is there a way to get exact (or at least repeatable) <5 degree rotations on parts in the SPH?  I've revised my design a bit by eliminating a bunch of fuel, and so it now flies faster (Mach 0.75 or so), but still at the bottom of the hump.  As I type, it's KER is showing just shy of 3 days' worth of fuel (and climbing, as the craft climbs and the thrust drops).

Putting AOA on you lifting surfaces just causes drag. Which decreases speed and fuselage AOA. So instead I suggest maybe 1 degree on the lifting surfaces. If you have to constantly pitch up to maintain level flight it means your wings arnt producing enough lift. So put on more wings until it stays level. I still don't know why you can't get above Mach 1.

[zolotiyeruki]

2 minutes ago, Gman_builder said:

Putting AOA on you lifting surfaces just causes drag. Which decreases speed and fuselage AOA. So instead I suggest maybe 1 degree on the lifting surfaces. If you have to constantly pitch up to maintain level flight it means your wings arnt producing enough lift. So put on more wings until it stays level. I still don't know why you can't get above Mach 1.

There's no pitching up here to maintain level flight--I shift fuel around so that minimal control is needed. With a 5 deg pitch on the wings, I suspect the problem is either A) too much L-I-D (if fuselage has 0 AoA), or B) too much parasitic drag (no LID, but now fuselage has AOA and higher drag).

I'll try using the rotate tool without any snapping, and see if I can get some improvements.  I'm playing with stock aero, FWIW.

[Gman_builder]

7 minutes ago, zolotiyeruki said:

There's no pitching up here to maintain level flight--I shift fuel around so that minimal control is needed. With a 5 deg pitch on the wings, I suspect the problem is either A) too much L-I-D (if fuselage has 0 AoA), or B) too much parasitic drag (no LID, but now fuselage has AOA and higher drag).

I'll try using the rotate tool without any snapping, and see if I can get some improvements.  I'm playing with stock aero, FWIW.

Honestly stock aero should make this even easier. If you use FAR it will tell you exactly what you need to do to make your plane fly and give you all the statistics and numbers on your aircraft.

[Van Disaster]

The seemingly randomly clipped parts around my craft are all aimed at reducing wave drag. I try not to clip tanks into other tanks although with mk2 parts that bothers me a little less as they have tons of free space given their resource capacity, and I'm wary of overlapping wing parts too much because FAR can get annoyed, but a little is ok.

FAR calculates drag by analysing the whole body shape, so any parts inside any other parts are ignored ( including the inside bits of half-clipped parts ). Wings are in a funny transition stage but still shape matters a lot there too.

As for why you're stuck at slow speeds, no idea what stock aero is really like but it's still very syrupy every time I try it. If you're really interested in aircraft you really should try FAR.